Late cenozoic magnetostratigraphy of Selkirk volcanics and associated sediments, west-central Yukon

Abstract

Brunhes, Matuyama, Kaena and Mammoth age basaltic lava (Selkirk Volcanics - TQS) as well as interbedded sediments were sampled in west-central Yukon Territory, Canada. Paleomagnetic sampling of basalt mapped as TQS along a 370 kilometre transect suggests that early eruptions of TQS occurred coevally over a significant distance to the north of Fort Selkirk. Basal basalt at Ne Ch'e Ddhawa pre-dates continental glaciation in Yukon and is older than the Fort Selkirk Vent (Lower Mushroom), previously thought to be the oldest eruptive vent at Fort Selkirk. The high confining pressures required to form pillow lava suggest subglacial eruptions at Mushroom section. An Early Pleistocene Fort Selkirk glaciation sequence (till and outwash) was reversely magnetized and assigned to the Late Matuyama chron between oxygen isotope stages 62 and 56 inclusive. A lateral moraine on Ne Ch'e Ddhawa was reversely magnetized and therefore assigned to one of the younger Pre-Reid glaciations. i